1. Field of the Invention
The present invention relates to screens and projection display apparatuses using the same, and more particularly to a screen and a projection display apparatus in which a scattering liquid crystal is used in addition to a conventional diffusing plate so that a gain (explained later) of the screen becomes variable.
2. Description of the Prior Art
FIG. 1 illustrates a conventional transmission screen 10, a projector 11 which emits image-forming rays of light 16, and an observer 12 who views an image displayed on the screen 1. The screen 10 includes a Fresnel lens 13, a diffusing plate 14 and a lenticular lens 15 integrated with each other.
The Fresnel lens 13 causes the image-forming rays of light 16 emitted by the projector 11 to converge. The diffusing plate 14 diffuses the rays of light output from the Fresnel lens 13 in a Y direction (the crosswise direction of the screen 10) and in a Z direction (the direction of the height of the screen 10). The lenticular lens 15 further diffuses the rays of light diffused by the diffusing plate 14.
Generally, the number of viewers or rightness of the surroundings vary depending on different circumstances in which the screen 10 is used, while the optical property of the conventional screen 10 is fixed and cannot be adjusted.
For this reason, there is a problem that the viewer may experience difficulty in viewing the image displayed on the screen 10.
Accordingly, an object of the present invention is to provide a screen and a projection display apparatus by which screen and apparatus the aforementioned problem is eliminated.
Another and more specific object of the present invention is to provide a projection display apparatus in which screen and a scattering liquid crystal is used, in addition to a conventional diffusing plate so that the gain of the screen becomes variable.
In order to achieve these objectives, the present invention provides a screen including a gain controller for changing a ratio (gain) of luminance at a light-outgoing face of the screen to luminance at a light-incident face of the screen. According to the screen of the present invention, the observable area can be changed to be best adapted to the condition in which the screen is used.
The present invention also provides a screen, wherein the gain controller includes: a pair of transparent electrodes opposite to each other; a scattering liquid crystal disposed between the pair of transparent electrodes; and a voltage regulator for adjusting a voltage applied to the pair of transparent electrodes. According to this aspect of the present invention, the gain of the screen can be stably controlled by adjusting the gain of the scattering liquid crystal.
Alternatively, the screen may include a Fresnel lens at which an image-forming light is incident on the screen; and a lenticular lens from which the image-forming light outgoes from the screen, wherein the gain controller may be disposed between the lenticular lens and the Fresnel lens. In another alternative constitution, the gain controller is provided to face the surface of the Fresnel lens from which surface the image-forming light outgoes, and the scattering liquid crystal constituting a part of the gain controller has a lenticular lens surface on its face from which face the image-forming light is output. According to these aspects of the present invention, the observable area can be changed to be best adapted to the condition in which the screen is used.
The present invention also provides a screen further including a transparent base which has a surface having discrete depressions, the surface facing the Fresnel lens, wherein the gain controller is provided on the surface of the transparent base which surface faces the Fresnel lens, and the scattering liquid crystal constituting a part of the gain controller has a lenticular lens surface on its face from which face the image-forming light is output. According to this aspect of the present invention, the distance between the liquid crystal and the lenticular lens surface is virtually zero. As a result, it is possible to display an image with higher resolution than a screen in which a separate lenticular lens is provided.
Alternatively, the screen may include a reflecting layer for reflecting the image-forming light emitted by a projector, and the gain controller is provided between the projector and the reflecting layer. According to this aspect of the present invention, the observable area can be changed to be best adapted to the condition in which the screen is used.
The present invention also provides a screen further including a brightness detector for detecting brightness of the surroundings, wherein an output from the brightness detector is used to operate the gain controller. According to this aspect of the present invention, it is possible to adjust the brightness of a displayed image in accordance with the variation of the brightness of the surroundings so that it becomes easier for a viewer to view the display.
The present invention also provides a projection display apparatus including: a body; a projector provided in the body; and a screen attached to the body, the screen comprising a gain controller for changing a ratio (gain) of luminance at a light-outgoing face of the screen to illuminance at a light-incident face of the screen.
Preferably, the gain controller of the screen of the projection display apparatus includes: a pair of transparent electrodes opposite to each other; a scattering liquid crystal disposed between the pair of transparent electrodes; and a voltage regulator for adjusting a voltage applied to the pair of transparent electrodes.
Preferably, the screen further comprises: a Fresnel lens at which an image-forming light is incident on the screen; and a lenticular lens at which the image-forming light is output from the screen, and the gain controller is disposed between the lenticular lens and the Fresnel lens.
Preferably, the gain controller is provided to face the surface of the Fresnel lens from which surface the image-forming light is output, and the scattering liquid crystal constituting a part of the gain controller has a lenticular lens surface on its face from which face the image-forming light is output.
Preferably, the screen further includes a transparent base which has a surface having discrete depressions, the surface facing the Fresnel lens.
Preferably, the screen further includes a brightness detector for detecting brightness of the surroundings, and an output from the brightness detector is used to operate the gain controller.
The present invention also provides a projection display apparatus including: a body; a projector provided in the body; and a screen having a gain controller for changing reflecting capability of the screen, wherein the screen further includes a reflecting layer for reflecting the image-forming light emitted by the projector, and the gain controller is provided between the projector and the reflecting layer.
Preferably, the screen of the above projection display apparatus further includes a brightness detector for detecting brightness of the surroundings, and an output from the brightness detector is used to operate the gain controller.
The present invention also provides a display method in a projection display apparatus having a projector and a screen, wherein the screen has a gain controller, the display method including the step of: adjusting a gain of the screen by using the gain controller.
Preferably, the gain controller employed in the display method has a scattering liquid crystal being disposed between a pair of transparent electrodes, and the adjusting of the gain being carried out by adjusting a voltage applied to the pair of transparent electrodes.